The present invention relates to assembly of devices and systems. More specifically, the present invention relates to self-assembly and related processes and the resultant devices.
Self-assembly refers in general to processes for assembling devices or components in which the assembly takes place without active interaction from an external force. Instead, self-assembly techniques rely on characteristics of individual components that urge the components to assemble together in a desired manner.
Self-assembly techniques are desirable because they can greatly reduce manufacturing costs. Further, they are particularly well suited for assembly of very small components, such as micro and nanometer sized components, in which their extremely small size makes physical and robotic assembly difficult.
Robotic assembly lines are (i) ineffective in assembling components that are smaller than 1 mm in size fundamental challenges appear at <100 μm length scale, as a result, components are connected on a board level not a chip level, and system performance goes down; (ii) are ineffective in assembling components in three dimensions; (iii) are ineffective in forming interconnects between non-planar and three-dimensional structures; (iv) have a limited throughput due to the serial nature of robotic pick and place; and (v) require a large capital investment.
Previous demonstrations of directed self-assembly to generate functional electrical microsystems include the coplanar integration of segmented integrated circuit (IC) devices into 2D “superchips” using capillary forces by Fung and Sliwa (see, C. D. Fung, P. W. Cheung, W. H. Ko, D. G. Fleming, Micromachining and Micropackaging of Transducers (Elsevier, Amsterdam, 1985, 1985) and J. W. Sliwa Jr., in US Patent. (1991), vol. U.S. Pat. No. 5,075,253); shape-directed fluidic methods that position electronic devices on planar surfaces using shape recognition and gravitational forces (see, A. Stemmer, H. Jacobs, H. F. Knapp, Proceedings of the SPIE—The International Society for Optical Engineering 2906, 80-5 (1996); and M. Sitti, H. Hashimoto, Advanced Robotics 13, 417-436 (1999)) by Smith and Yeh (see, H. J. J. Yeh, J. S. Smith, IEEE Photonics Technology Letters 6, 706-708 (1994) and J. S. Smith, H. J. J. Yeh, U.S. Pat. No. 5,824,186 (1998)); liquid-solder-based self-assemblies that use the surface tension between pairs of molten solder drops to assemble three-dimensional electrical networks, ring oscillators, and shift registers (see, C. Baur et al., Nanotechnology 9, 360-364 (1998). And L. T. Hansen, A. Kuhle, A. H. Sorensen, J. Bohr, P. E. Lindelof, Nanotechnology 9, 337-342 (1998).) by Whitesides and Jacobs; capillary force directed self-assembly that uses hydrophobic-hydrophilic surfaces patterns and photo curable polymers to integrate micro-optical components, micromirrors and semiconductor chips on silicon substrates (see, R. Resch et al., Applied Physics a 67, 265-271 (1998); P. E. Sheehan, C. M. Lieber, Nanotechnology 7, 236-240 (1996); P. Kim, C. M. Lieber, Science 286, 2148-2150 (Dec. 10, 1999)) by Boeringer and Howe; and solder-receptor directed self-assembly where metal contacts on segmented semiconductor devices bind to liquid-solder-based-receptors to assemble and electrically connect devices on planar and non-planar surfaces (see, J. Fraysse, A. Minett, O. Jaschinski, C. Journet, S. Roth, Vide-Science Technique et Applications 56, 229−+ (2001)) by Jacobs and Whitesides. The shape-directed method by Smith and Yeh (see, A. Stemmer, H. Jacobs, H. F. Knapp, Proceedings of the SPIE—The International Society for Optical Engineering 2906, 80-5 (1996); and M. Sitti, H. Hashimoto, Advanced Robotics 13, 417-436 (1999)) is used by Alien Technology (www.alientechnology.com) to direct the assembly of small radio frequency identification tags. They flow suspended semiconductor chips over a surface that carries correspondingly-shaped “holes” that act as receptors for the device components. The device components settle into these holes due to gravitational forces. The process by Fung and Sliwa uses segmented integrated circuits that float at an air-liquid or liquid-liquid interface (FIG. 2). The circuit segments are pulled together due to the reduction of the interfacial free energy of the system.
There will be no universal self-assembly strategy that can solve every engineering problem. For example, the processes by Smith and Yeh and Fung and Sliwa allow the formation of two-dimensional assemblies; their extension into three dimensions, however, appears to be impossible. Both strategies do not address the formation of electrical interconnects during the assembly step and require additional processing.
There is an ongoing need to improve self-assembly techniques and expand their functionality.